Which of these four questions arising from modern ideas of force and matter is one of the great unanswered questions of contemporary science? Group of answer choices Why do planets move in elliptical orbits? What is force? Why are the inertial mass (defined in Newton's second law) and the mass used in his law of gravitation identical? Why is Mercury's orbit measurably different from that predicted by Newton's laws?
a) Why do planets move in elliptical orbits?
b) What is force?
c) Why are the inertial mass and the mass used in gravitation identical?
d) Why is Mercury's orbit different from Newton's predictions?